Field of the Invention
The present invention relates to a method of detecting clogging of a chuck table that holds a workpiece such as a wafer or the like under suction thereon, and a processing apparatus for processing a workpiece such as a wafer or the like.
Description of the Related Art
A grinding apparatus and a cutting apparatus for processing a wafer as a workpiece have a chuck table for holding the wafer under suction thereon (see, for example, Japanese Patent Laid-open No. 2015-60922). The chuck table has a holding surface made of a porous material and held in fluid communication with a suction source. The holding surface holds the wafer under suction thereon.
If the holding surface of the chuck table or the inside of the chuck table is clogged with a contaminant such as ground or cut chips, then when the wafer is held on the chuck table under suction, the suction force acting on the wafer through the clogged region of the holding surface tends to become weak, failing to hold the wafer securely on the holding surface. While the wafer is being processed, therefore, chips may jump off the wafer on the chuck table, or the quality of the processed wafer may be adversely affected. It has heretofore been the practice for the operator to check whether a chuck table is clogged or not before a wafer is ground or cut on the chuck table. If the operator finds the checked chuck table to be clogged beyond an allowable level, then the operator replaces the chuck table with another chuck table or performs an appropriate process to remove the clogging substance from the chuck table.
According to one conventional way of checking a chuck table for clogging, the operator applies water and air at the same time to the holding surface of the chuck table while it is developing suction, and visually inspects the holding surface to see if there is any region of the holding surface where no bubbles are produced. Specifically, since no bubbles are produced in a region that is clogged with a contaminant, the operator can visually determine that the region is clogged if there are no bubbles in the region during the inspection.